Dr Kelly had been named by the government as the possible source for a controversial BBC story on Iraq.

US intelligence officials are said by the New York Times to be wary about making any final judgments about the new evidence in North Korea.

They are keenly aware that, as in Britain, assessments of Iraq's nuclear programme have sparked a national debate over whether intelligence was exaggerated, and have cast doubts on all the agency's findings, the paper says.

While on his brief visit to Seoul, Mr Blair will hold talks with South Korean President Roh Moo-hyun.

They will discuss the threat from North Korea as well as economic relations.

South Korean officials say they hope Mr Blair can use his influence on the world stage to encourage a diplomatic solution.

Mr Blair is backing the United States in its demand for negotiations involving all key players in the region.